Centrifugal compressor

ABSTRACT

A centrifugal compressor includes a housing having a part joint plane which extends parallel to or along a machine axis, and a shaft extending along the machine axis and having a first shaft end and a second shaft end. At least one impeller is mounted on the shaft. A collector helix is arranged downstream of the at least one impeller and collects the compressed fluid prior to an outflow into a following machine module. The collector helix is arranged on the first shaft end. A drive is arranged on the first shaft end. An axial intake at an overhang stage of the centrifugal compressor is provided on the shaft on the second shaft end. The collector helix is realized as a single piece in the circumferential direction and is flanged to the housing of the centrifugal compressor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Stage of International ApplicationNo. PCT/EP2011/057660, filed May 12, 2011 and claims the benefitthereof. The International Application claims the benefits of Germanapplication No. 10 2010 020 891.4 DE filed May 18, 2010. All of theapplications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a centrifugal compressor having a shaft whichextends along a machine axis, there being a drive on the side of acollector helix, which collects a compressed fluid downstream of atleast one impeller upstream of an outflow into a following machinemodule, which drive is arranged on a shaft end which is guided out of ahousing of the centrifugal compressor, wherein an axial intake isprovided on an overhang stage of the centrifugal compressor on anopposite shaft end of the shaft.

BACKGROUND OF INVENTION

These types of compressors are used in particular for compressing largevolume flows (e.g. 600,000 m³ per hour) at pressures of, for example, 8bar. The advantage of the axial intake, in this case, is that the intakesurface is particularly large and at the same time the maximum diameterof the impellers remains moderate such that the machine can be operatedat higher speeds without overloading the materials of the rotatingparts. Said machines are particularly preferred for air compression.

In the so-called collector helix, the compressed process fluid iscollected behind the impeller and flows into a machine moduledownstream, for example a cooling unit. As a rule, such a collectorhelix is an annular chamber realized in a slightly helical manner, thecross sectional area of which widens in the circumferential direction asit gets closer to the outlet into the following unit in the direction ofrotation. Said expensive geometry is due to the fact that unfavorableflow contours, which generate high pressure losses in the collectorchamber, are also particularly damaging for the efficiency as a resultof the increased density of said fluid. In the case of conventionalcompressors, the collector helix, just as the housing, has a horizontalpart joint which either generates an unfavorable deposition in the flowcontour of the collector helix, which leads to pressure losses, orrequires expensive finishing which has to be carried out in atime-intensive, individualized manner on the element which is realized,as a rule, as a cast part.

Documents DE 38 35 341 A1 and U.S. Pat. No. 2,578,617 A already makeknown centrifugal compressors with an opening for compressing a fluid,said centrifugal compressors having a housing which has a part jointplane, which extends parallel to a machine axis and has a shaft whichextends along the machine axis, having at least one impeller and onecollector helix which is arranged downstream of the at least oneimpeller and collects the compressed fluid upstream of an outflow into afollowing machine module, wherein the collector helix is arranged on thefirst shaft end. In addition, the apparatuses disclosed in saiddocuments include a drive which is arranged on the first shaft end,wherein an axial intake of the centrifugal compressor is provided on thesecond shaft end.

SUMMARY OF INVENTION

Consequently, it is the object of the invention to improve thecentrifugal compressor defined in the introduction in such a mannerthat, on the one hand, production expenditure is reduced and, on theother hand, no high pressure losses are generated in the collectorhelix.

It is proposed as claimed in the invention that the helix is realized asa single piece in the circumferential direction and is flanged to thehousing of the centrifugal compressor.

The advantage of the collector helix being realized in a single piece isthat the helix, which is realized as a rule as a cast part, does notform any deposition generated by a part joint on the flow contour whicheither leads to unwanted pressure losses as a result of a disturbance inthe flow or requires an expensive individualized finishing process.

Besides this, the advantage of realizing the helix in a single piece isthat as a result of the high pressure of the outgoing fluid, the helixis deformed most extensively in a rotationally symmetrical manner andnot, as in the case of conventional designs, severely distorted by theseparation in a part joint. In particular, no part joint is opened as aresult of the outgoing pressure and there is also no ovalizing of theflange or of the connecting diameter of the collector helix, realized asa rule in a round manner.

An advantageous further development of the invention provides that thehelix is realized as support of a shaft bearing for the bearingarrangement of the shaft. As a result, on the one hand a particularlycompact design is achieved and, on the other hand, the tolerance chainbetween the impellers of the shaft and opposite inside surfaces of thehousing is particularly short.

Additionally advantageous is a design of the collector helix as carrierof a shaft seal on the side of that shaft end on which the drive of thecentrifugal compressor is arranged and the shaft is guided out of thehousing of the centrifugal compressor. In particular in combination withthe design of the helix as carrier of the bearing, there is aparticularly short tolerance chain between the bearing arrangement ofthe shaft and the surfaces of the seal which are opposite the shaft suchthat particularly small seal clearances can be realized or the seal hasa particularly low degree of laxity.

In an expedient manner, the collector helix is realized as a componentclosing off the housing of the centrifugal compressor on the one sidesimilar to a cover. The number of components is reduced correspondingly.

The directional specifications—axially, radially and circumferentialdirection—always relate to the machine axis.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below in more detail by way of a specialexemplary embodiment with reference to a drawing, further possibilitiesof the conversion of the invention presenting themselves to the expertapart from said exemplary embodiment in particular from an arbitrarycombination of the features defined in the dependent sub-claims. Inwhich drawing:

FIG. 1 shows a schematic representation of a longitudinal sectionthrough a compressor as claimed in the invention.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a schematic longitudinal section through a compressor CO asclaimed in the invention. Essential component parts of the compressor COare a housing C, a shaft SH, the impellers IM—only one of which is shownand supports an overhang stage ST, a collector helix CC which is flangedto the housing C and a drive D which rotates the shaft SH.

The shaft SH extends along a machine axis AX which is at the same timethe axis of rotation of the drive D. A process fluid F is sucked inaxially by the compressor CO and enters into an overhang stage ST,continues to be compressed downstream by means of the impellers IM andenters into a last stage LST in order to be collected finally in thecollector helix CC for entry into the machine module downstream. Theshaft SH is mounted in two radial bearings BE1, BE2. The shaft SH has afirst shaft end SE1 and a second shaft end SE2, the first shaft end SE1being driven by the drive D and the second shaft end SE2 carrying theoverhang stage ST. The term shaft end SE1, SE2 in the invention refersto a region of the shaft which extends from the respective end of theshaft in the direction of the shaft center, approximately a third of theoverall shaft length being designated in each case as the shaft end inthe terminology of the invention. Apart from the torque-transmittingconnection to the drive D, the collector helix CC, the second radialbearing BE2 and a shaft seal SHS are also arranged in the region of thefirst shaft end SE1. Whilst the housing C has a part joint in theextension of the machine axis AX, the collector helix CC is in one piecein the extension of the machine axis or parallel thereto and is flangedto the housing C by means of first fastening elements SM1. At the sametime, the collector helix CC is carrier of the second radial bearing BE2and of the shaft seal SHS. The advantage of the one-piece design of thecollector helix, which is realized as a cast part, is that saidcollector helix in the circumferential direction does not have anydeposition, brought about otherwise by a part joint which could causeflow losses. The fastening of the second radial bearing BE2 and of theshaft seal SHS to the collector helix CC results in as short a tolerancechain as possible between the radial bearing BE2 and the shaft seal SHSsuch that radial clearances of the shaft SH in the shaft seal SHS,necessary for example for thermal expansion, are able to be minimal.Particularly good efficiency can be achieved in this way.

1-2. (canceled)
 3. A centrifugal compressor for compressing a fluid, thecentrifugal compressor comprising: a housing which has a part jointplane which extends parallel to or along a machine axis, a shaft whichextends along the machine axis and has a first shaft end and a secondshaft end, at least one impeller which is mounted on the shaft, acollector helix which is arranged downstream of the at least oneimpeller and collects the compressed fluid prior to an outflow into afollowing machine module, wherein the collector helix is arranged on thefirst shaft end, and a drive which is arranged on the first shaft end,wherein an axial intake at an overhang stage of the centrifugalcompressor is provided on the shaft on the second shaft end, wherein thecollector helix is realized as a single piece in the circumferentialdirection and is flanged to the housing of the centrifugal compressor.4. The centrifugal compressor as claimed in claim 3, wherein thecollector helix is realized as support of a radial bearing for thebearing arrangement of the shaft.